Commitments and Contingencies - Additional Information (Detail) $ in Thousands	3 Months Ended		12 Months Ended
	Sep. 28, 2018 USD ($)	Sep. 30, 2016 USD ($)	Sep. 28, 2018 USD ($) Person	Sep. 29, 2017 USD ($)	Sep. 30, 2016 USD ($)	Mar. 31, 2014 USD ($)
Contingent Liabilities [Line Items]
Rental expense for operating leases for engineering, selling, administrative and manufacturing			$ 17,900	$ 17,700	$ 19,000
Total penalty proposed by DTCC Office of Compliance						$ 20,000
Penalty suspended and eligible for offset credit						10,000
Penalty suspended and approved for offset credit						$ 10,000
Insurance recovery received		$ 5,000	$ 0	$ 7,789	$ 5,000
Facility cleanup costs net of insurance recoveries	$ 2,500
US
Contingent Liabilities [Line Items]
Number of employees represented by various labor unions | Person			679
Percentage of employees represented by labor unions			17.00%